Uncatalyzed and acid-aided microwave hydrothermal carbonization of orange peel waste

•Orange peel waste is suitable to be treated by microwave hydrothermal carbonization.•Citric acid catalyst resulted in 30% higher hydrochar yield.•Citric acid produces hydrochar with higher C content, calorific value and nanospheres.•Citric acid catalyst promotes the formation of nanospheres in hydr...

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Bibliographic Details
Published in:Waste management (Elmsford) 2021-05, Vol.126, p.106-118
Main Authors: Lei, Qian, Kannan, Shrikalaa, Raghavan, Vijaya
Format: Article
Language:English
Subjects:
Citric acid
Hydrochar
Hydrothermal carbonization
Microwave
Orange peel waste
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Summary:•Orange peel waste is suitable to be treated by microwave hydrothermal carbonization.•Citric acid catalyst resulted in 30% higher hydrochar yield.•Citric acid produces hydrochar with higher C content, calorific value and nanospheres.•Citric acid catalyst promotes the formation of nanospheres in hydrochar. Orange, one of the most important fruit categories to be consumed across the world, when processed produces 50% of its weight as waste. Current waste management options for orange peel waste are inadequate to use the waste in wholesome and its disposal might lead to other environmental concerns. Here, we present microwave hydrothermal carbonization as an alternative to utilize the orange peel waste. Further, using citric acid to catalyze the microwave hydrothermal carbonization resulted in 30% higher maximal yield of hydrochar, and the hydrochar produced had better elemental, proximate and energy properties than hydrochar made during uncatalyzed microwave hydrothermal carbonization. Further, structural analysis revealed that citric acid promoted the formation of nanospheres during microwave hydrothermal carbonization. Taken together, microwave hydrothermal carbonization of orange peel waste using citric acid as a catalyst might not only help address the waste management concerns for orange peel waste, but also can produce end products of potential commercial value.
ISSN:0956-053X
1879-2456
DOI:10.1016/j.wasman.2021.02.058